A feature of the present invention to provide a disc brake arrangement of the type designated at the outset, in which residual drag moments are largely suppressed in any operating mode, in order thereby to improve the functionality in a simple manner, with low production costs.
This feature is achieved by a disc brake of the type designated at the outset, in which it is provided that the actuating piston is coupled to the mechanical actuator via an elastically deformable driving arrangement, wherein, as a consequence of a relative displacement between the actuating piston and the actuator, the driving arrangement provides a restoring movement in accordance with its elastic deformation.
According to the invention, the previously mentioned rollback function is dissociated from the seal between the housing and the actuating piston and is assigned instead to the driving arrangement between the actuating piston and the mechanical actuator. This has the advantage that, in the case of a movement of the mechanical actuator as a consequence of an actuation for the purpose of actuating the parking brake, the driving arrangement is deformed elastically in each case and a rollback function, i.e. drawing back of the actuating piston, can thus be provided. As a result of the brake lining being attached to the actuating piston, for example by means of a fastening spring, the brake lining can be actively drawn back together with the actuating piston. Otherwise, a non-attached brake lining can separate from the brake disc, for example because of the dynamic vibratory forces during travel.
In a development of the invention, it can be provided that the driving arrangement is accommodated with a friction fit in the actuating piston and is movable relative to the mechanical actuator, wherein the mechanical actuator provides a limited movement region in which the driving arrangement is accommodated and is displaceable. It is thereby ensured that the driving arrangement acts on the actuating piston with sufficient forces and therefore provides a driving function in accordance with the current position of the mechanical actuator. The friction fit is realized in such a way that, in the case of sufficiently large forces, with a particular elastic deformation of the driving arrangement being achieved, the static friction of the friction fit is overcome and, ultimately, a relative movement between the driving arrangement and the actuating piston is permitted. What is determinant, however, is that, before attainment of a threshold value at which the static friction is overcome and the actuating piston slips relative to the driving arrangement, there is a sufficiently great elastic deformation of the driving arrangement.
In respect of the movement region, it can be provided that the latter is realized so as to be greater than the axial length of the driving arrangement. This allows a certain movement clearance, in addition to the amount of the elastic deformation of the driving arrangement between the actuating piston and the mechanical actuator. In this context, it can be provided that the distance by which the movement region is realized so as to be greater than the axial length of the driving arrangement determines a functional clearance that is dimensioned in such a way that it provides a restoring movement of the actuating piston as a consequence of a hydraulic brake actuation. Owing to this functional clearance, it is possible, as a consequence of a hydraulic brake actuation, for the actuating piston to be repeatedly guided strongly back in the direction of its initial position, in such a way that the braking action is actually removed and there are no longer any residual drag moments.
In respect of the structural design of the disc brake according to the invention, it can be provided that the movement region is delimited by a flange realized on the mechanical actuator and/or by a stop, in particular a retaining ring, that can be attached to the actuator. In particular, it can be provided that, on at least one side of the movement region, the flange or/and the stop is/are provided with a surface contour whose geometry is realized to achieve a desired deformation of the driving arrangement, for example having a bevel. The selective configuration of the surface contour is particularly appropriate on the side of the movement region that is near the brake lining. In this region, the driving arrangement is deformed in a manner intended to ensure that an automatic restoring movement occurs in order to prevent residual drag moments. A further measure in respect of the configuration of the surface contour is that of avoiding contour shapes that promote wear, in particular edges, which can negatively affect the service life of the driving arrangement.
As already indicated above, it can be provided that the mechanical actuator can be actuated electromechanically, in particular via a spindle drive that can be motor-controlled.
In respect of the driving arrangement, it is possible for the latter to comprise a ring made of elastically deformable material, in particular a rubber ring. A simple and inexpensive variant is obtained, for example, if it is provided that the ring made of elastically deformable material is disposed directly or indirectly, via a guide ring or control ring connected to the latter, in a movable manner on the actuator. As an alternative to this, in the case of one embodiment of the invention it can be provided that the driving arrangement has a spring element, which biases a rigid driving ring into a predefined initial position. The control ring in this case can be disposed, largely without friction and with radial clearance, on the actuator, within the movement region. For the purpose of simple assembly, in the case of this embodiment variant it is appropriate for at least one removable retaining ring to be arranged as a stop. The ring made of elastically deformable material is connected to the control ring by, for example, adhesive bonding or by being vulcanized on.
As a further alternative embodiment of the invention, it can be provided that the driving arrangement has a spring element that biases a rigid driving ring into an initial position. In this case, it is possible for the spring element to comprise a coil spring, spiral spring or disc spring. In this case, again, the driving ring, which is realized as a rigid element, for example composed of a plastic or metal part, has a friction fit with the actuating piston.
As already indicated above, the rollback function, in particular for actuation of the parking brake, is realized, according to the invention, in the region between the actuator and the actuating piston. Accordingly, in the case of a preferred development of the invention, it can be provided that disposed between the actuating piston and the housing there is a hydraulic seal arrangement, which remains substantially without deformation in the case of an actuation in the direction of actuation. This means that, in the case of this embodiment variant, the rollback function remains largely suppressed in the region of the hydraulic seal between the actuating piston and the housing.
Other advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings.